Heretofore, in an air-conditioning apparatus such as a multi-air-conditioning system for a building, a refrigerant circuit is constituted and a refrigerant is circulated by connecting pipes between an outdoor device (outdoor unit), which is a heat source device installed on the outside of the building, and indoor devices (indoor units) installed inside the building, for example. An air-conditioned space is then heated or cooled by utilizing heat rejection and heat removal of the refrigerant to heat or cool air.
In such a multi-air-conditioning system for a building, a plurality of indoor units is connected by pipes, and there is often a mixture of stopped indoor units and running indoor units. The pipes that connect the outdoor unit to the indoor units may also reach 100 m, for example. As the pipes become longer, more the refrigerant fills the air-conditioning apparatus.
The indoor units of such a multi-air-conditioning system for a building are typically disposed and used in indoor spaces where people are present (such as office spaces, rooms, and stores, for example). At this point, if for some reason refrigerant leaks out of an indoor unit disposed in an indoor space, the refrigerant may be flammable or toxic depending on the refrigerant type, thus posing a serious problem from the perspective of the effects on and the safety of the human body, for example. In addition, even assuming that the refrigerant is not harmful to the human body, for example, the refrigerant leakage is expected to lower the oxygen concentration in the indoor space and exert an adverse influence on the human body.
Consequently, there has been proposed a system that suppresses the quantity of refrigerant leaking indoors by providing the outdoor unit with a refrigerant leakage sensor and a pipe shutoff valve, such that refrigerant does not flow out of the outdoor unit if a refrigerant leak occurs (see Patent Literature 1, for example).